€¦ · Web view · 2014-12-22studied uses of high copper amalgam alloys in dentistry , ......

Journal of Babylon University/Engineering Sciences/ No.(4)/ Vol.(22): 2014

The Effect of Admixing Al2O3 on Some Properties of High Copper Dental Amalgam

Jassim Mohammed SalmanUniversity of Babylon, College of Materials Engineering

Department of Metallurgy EngineeringE-Mail: jmsmaterials @yahoo.com

ABSTRACT In recent years, there have been many attempts to improve properties of dental amalgam. The aim of this study is to investigate the effect of additional Al2O3 on properties of high copper dental amalgam. Al2O3 is added in different percentages ( 0.1, 0.2, 0.3, and 0.4wt% ). The specimens were prepared according to A.D.A specification No. 1. The specimens have been stored at 37±1 Cº by using glass chamber prepared for this purpose. The prepared specimens are characterized by different types of tests such as creep,hardness,dimensional change ,microstructure by optical microscopic and corrosion test. The results show that the hardness increase with increasing Al2O3 percentage . Results of creep resistance are within the approved percentage of A.D.A., dimensional change is less than the approved percentage by A.D.A. also. The best corrosion resistance is at 0.2 and 0.4wt% of Al 2O3 with improving ( 60 %) and (55 %) respectively.Keywords: Dental Amalgam, Admixed Al2O3, High Copper

: الخالصة من الهدف, االخيرة السنين في االسنان ملغم سبائك خواص لتحسين عديدة محاوالت هنالك كانت

تم. النح88اس عالية النحاس ملغم سبيكة خواص بعض على االلمنيوم اوكسيد اضافة تأثير لبيان هو الدراسة هذه رقم) المواصفة حسب العينات حضرت (.8 0.1,0.2,0.3,0.4) مختلفة مئوية بنسب االلمنيوم اوكسيد اضافة

. الغ88رض له88ذا مع88ده زجاجيه حج8رة في 37 ح8رارة بدرجة العين88ات حفظ تم. لألسنان األمريكية للجمعية(8 1 المجهرية البنيه, باألبعاد , التغير الصالدة, مثل: الزحف الفحوصات من مختلفة ألنواع المحضرة العينات اعدت

.التآكل وفحص الض888888888888888888888888888888888888888888888888وئي المجهر بواس888888888888888888888888888888888888888888888888طة.

ض8من الزحف مقاومة , نت8ائج المض8اف االلم8نيوم اوكس88يد نسب بزي8ادة الصالدة قيم في زياده النتائج اضهرت ك88انت تآكل مقاومة باألبع88اد. افضل التغ88ير وك88ذلك لألس88نان األمريكية الجمعية قبل من بها المس88موح النسب .التوالي على (55)% و ( 60) % مقداره وبتحسن 0.4و 0.2 االلمنيوم اوكسيد لنسب

, عالي االلمنيوم اوكسيد , اضافة االسنان ملغم: مفتاحيةال الكلمات Introduction

Dental amalgam is a metallic alloy formed by the reaction of mercury with a powder alloy containing silver (40–70%), tin (15–30%) and copper (10–30%), and sometimes a small percentage of zinc[ N.Tolou et. al., 2013] and dental amalgam is the most widely used restorative material. The silver alloy is a fine powder that is composed mostly of silver, tin and copper.

When the silver alloy and mercury are mixed, a chemical reaction occurs that forms dental amalgam. This reaction between the alloy and mercury is termed as amalgamation reaction. Although some forms of mercury are hazardous, the mercury in the amalgam is chemically bound to the other metals to make it stable and therefore safe for use in dental applications.[Akram et. al., 2012]. For many years, the amalgamation of silver with mercury to produce a condensable mixture which could be used to restore various defects in teeth followed a tortuous path of negative results However, at the turn of the century, amalgam alloys having acceptable characteristics for successful clinical use emerged. From that point on, silver amalgam was widely accepted as the material of choice for low-cost, easily placed, and durable restorations.[Allan et. al., 1965 , A.Brett et. al., 2002 ]. Until now ,there have been many attempts to improve properties of dental

875


amalgam which comprise treatment of amalgam alloy powder or the additioned some materials.

Razavi et. al., 2011 studied the physical and mechanical properties of high copper and silver dental filling amalgam alloys and they found that adding more silver to the amalgam increased its compressive strength and creep resistance.

Gaurav, 2012 studied uses of high copper amalgam alloys in dentistry , the results showed that high copper was much more strength , corrosion resistance, durable and resistance to tarnish as compared to low copper amalgam.

Capelo et. al., 2014, study corrosion of two no noble dental alloys . The results obtained showed that galvanic cell obtained by coupling the two non-noble alloys presented had very low cell potential while the galvanic cell between one noble alloy showed a higher cell potential.

The purpose of this study is to investigate the effect of admixing Al2O3 on some properties of high copper dental amalgam. 2. Experimental Procedure 2.1.Materials

Ardent admixed amalgam powder alloy 44.5% Ag, 30% Sn and 25.5% Cu was used in this study is made in Sweden which purchased from the market is the master powder alloy used, It is high copper alloy. The shape of this powder is a mixture of irregular (atomized). Al2O3 powder of 99.99% purity and with 20 μm size is added to powder alloy in different percentages (0.1, 0.2, 0.3, and 0. 4 wt%).2.2. Specimens Preparation

The amalgams are mechanically mixed in a dental amalgamator type (YDM-pro)for 35 sec. according to the A.D.A instructions. The freshly prepared mixed is condensed with hand condensers into Teflon mold with dimensions of 4 mm in diameter and 8 mm in height. The mold is opened and the specimens are ejected.2.3. Microstructure Observation

The specimens are cold mounted and grinded with emery paper at the following sequence (600, 800, 1200, 2000, 2500) and polished with diamond past of particle size 0.25 µm then tested using optical microscope. Amalgam specimens were etched using the following solutions [C.Allan et. al., 1965] . Solution A Solution B "Hypo" Rinse4 gm. K2Cr2O7 4 gm. I Na2S2O3 .5H2O1 gm. KI 96 ml. ethyl Dissolved in water100 ml. H2O alcohol

The sample is swabbed with solution A for 20-40 seconds and rinsed with water. Then it is lightly swabbed with solution B for 5-15 seconds, followed with a "hypo" swab-rinse, washed with water, and dried.2.4 Creep

Creep test is conducted according to A.D.A. specification No. 1 [A.D.A, 1975] at 37± 1 Cº, where allows the maximum of 3% creep. The length of the specimen measured by a micrometer caliper. At three hours after the end of trituration the specimen is subjected to a constant axial pressure of 10 MN/m2. This load is maintained for 21 hours after which the specimen length is measured with the above mentioned.

2.5 Dimensional Change

876


Dimensional change is accomplished according to A.D.A. specification No.1 at 37± 1 Cº.The initial measurement is taken 30 minutes after the end of trituration. The final measurement is taken at the end of 24 hours. During this test, the temperature of the specimens is maintained at 37± 1 Cº. The dimensional change must be within range of ± 20 μm/cm.2.6 Vickers Hardness Test

Vickers hardness of the specimens is measured using hardness test devise type (Digital Display Microhardness Tester HVs-1000 ) at one week after the end of trituration. The applied load is 0.2 Kg for 10 seconds.2.7 Corrosion Test

Potentiostatic polarization is used as the technique for evaluating corrosion resistance for all amalgam alloys tested. Computerized potentiostate (type DY2323 Bi-Potentiostat, USA) is used for conducting the polarization test. The corrosion resistance of the amalgam specimens is studied in synthetic saliva, whose composition is shown in Table (1) [Marek, 1990], the pH solution was 6.7 at 37 Cº temperature. The specimens are tested after 1 week form the end of trituration. The surface area of the tested specimens 1cm2, the upper and lower surfaces of the cylinder specimens have been covered with epoxy.

The corrosion test cell used in this study was made according to [ASTM, 1988]. The corrosion cell is a beaker of (250)ml capacity with water jacket, the reference electrode is Standard Calomel Electrode (SCE), and Auxiliary Electrode (AUX.E.) is platinum electrode, a lugging capillary is kept in such a way that the working electrode (specimen) and its tip remain at a distance of about 1mm in between to avoid ohmic drop. The corrosion test is carried out at 37±1 Cº to stimulate the human body temperature by means of water jacket, which controlled by thermostatic water path.When the specimen reaches the constant potential, potentiostatic polarization is

started from an initial potential of 250 mv below the open circuit potential and the scan was continued up to 250 mv above the open circuit potential[ASTM, 1988], the scan potential may be more than this range when needed. The specimens are scanned in the positive direction at a sweep rate of 1 mV/ Sec and the current is reported to potential by computer. Corrosion rate measurement is obtained by using equation (1) [Fontana et. al., 1978].

Where:E.W. = equivalent weight (gm/eq).A = area (cm2)ρ = density (gm/ cm2)0.13=metric and time conversion factor. icorr. = current density (μA/cm2)3.RESULTS AND DISCUSSION Table 2 shows the results of creep ,dimensional change and hardness with different weight percentage of Al2O3. The creep values ( 0.23- 0.65) and these allowable creep percentage by A.D.A. is 3% [ A.D.A. 1975 ]. Creep is a slow change in shape caused by compression due to dynamic intra-oral stresses. Creep causes amalgam to flow, such that unsupported amalgam protrudes from the margin of the cavity. These

877


unsupported edges are weak and may be further weakened by corrosion. Fracture causes the formation of a ‘ditch’ around the margins of the amalgam restoration. Creep also creates overhangs on fillings leading to food trapping & secondary decay. The gamma-2 phase of amalgam is primarily responsible for the relatively high values of creep exhibited by some materials.[Robert and Craig,1992]. Creep percent is calculated by using the following equation [ A.D.A.1975] .

whereLº = original length (mm).L = final length (mm).

Dimensional change according to A.D.A specification No.1 must be within range of ± 20µm/cm.[ A.D.A 1975 ].The dimensional change of all amalgams within limit(see table 2).Dimensional change is affected by many factors, such as the mercury/alloy ratio as well as trituration and condensation techniques. During amalgamation reaction expansion and contraction occur simultaneously. The dissolution of gamma particles generally leads to contraction, whereas the formation of gamma-1 causes expansion. The overall dimensional change is therefore the sum of these two processes. Improper manipulation that alters the ratio of gamma to gamma-1 and η in the set amalgam therefore also will alter its dimensional change[ M.Igiesias et. al., 1984 ].

The effect of Al203 on hardness are summarized in table 2.The table shows that the hardness increase with increasing Al2O3 percentage .The highest hardness value is (Am-0.4) and the lowest value is (Am-0).

Figures 1,2,3,4 and 5 show the polarization behaviors of amalgams in synthetic saliva at 37±1 Cº with different percentage weight of Al2O3 ( 0,0.1,0.2,0.3 and 0.4wt%).The polarization tests are carried out by using potentiostatic equipment on amalgam specimens of dimensions of 4 mm in diameter and 8 mm in length. The corrosion parameters are obtained from these figures are Ecorr, Icorr, and corrosion rate. Figure (1) shows cathodic and anodic polarization curves of the amalgam (Am-0) in synthetic saliva solution. It indicates that the corrosion parameters of this amalgam (Ecorr, Icorr, and corrosion rate) are -535.8 mV, 1.27 µA and 0.97 mpy respectively. The anodic polarization behavior of this amalgam is active due to an increase in current density which leads to amalgam dissolution after the corrosion potential has passed until reaching the last part of polarization curve where the current density is reduced indicating the critical current density, and then it remains constant due to barrier film formation, which is similar to that observed by other investigators. [M.Fathi et. al., 2004. ] .

Figure (2) shows polarization behavior of Am-0.1 amalgam. The corrosion current density(2.21 µA) has more value than the current of Am-0(1.27 µA) amalgam, so it has a low corrosion resistance.

Figures (3-5) show the polarization behaviors of Am-0.2, Am-0.3 and Am-0.4 with weight percentage of Al2O3 (0.2,0.3,and 0.4)respectively. The figures show that the presence of Al2O3 improves corrosion resistance because of reduction in corrosion current density. This can be seen in table (3) which indicates the improvement in corrosion resistance due to increase in Al2O3 content.

878


The improvement percentage is shown in table(3). The highest corrosion current is of amalgam (Am-0.1) (2.21 µA), and the lowest corrosion current of (Am-0.2) amalgam is (0.51µA). The corrosion current of amalgam(Am-0) is (1.27 µA). In general there is considerable reduction in corrosion current density for the amalgam containing Al2O3 ,which leads to improvement in corrosion rate as shown in table (3). It can be seen from the table that the improvement percentage (in case of amalgam with Al2O3 increases with increasing Al2O3 content. These results give an indication for forming the passive film which leads to improvement in corrosion resistance of amalgam. The maximum improvement percentages is 60 % of Am-0.2 amalgam which contains 0.2 wt%Al2O3.Figure 6 shows the microstructure of amalgams with different weight percentage of Al2O3. The matrix of the amalgam is γ1 phase ( white regions), the black regions are the η phase (Cu6Sn5) and the unreacted particles dark gray regions which consist of γ phase (Ag3Sn) and ε phase Cu3Sn. [C.Allan et. al., 1965]. 4. CONCLUSIONS:1- The small amounts of Al2O3 improved the properties and corrosion resistance.2- The best addition of Al2O3 to amalgams is 0.2 wt.%.3- Dimensional change of amalgams is less than A.D.A. allowable limit.4- The obtained results from creep in the specimens show that high creep resistance.5- It is observed that the Vickers hardness increases with increasing Al2O3 percentage.

5. ReferencesBret, A. A. Acciani, and C. Antonio, 2002, ''Corrosion of Dental Amalgams'', Key

Engineering Materials Vol.230-233, pp. 463-466.Akram, Seyed and Laieh, 2012, ''Effect of Copper Content on Compressive Strength and

Microstructure of Dental Amalgams'' , Engineering, Vol.4, pp.155-159.Allan , C.1965,''Microstructure of Dental Amalgam'' J. Den. Res, Vol.4, NO. 5.Capelo,2014,''Galvanic Corrosion of Two Non noble Dental Alloys.'' Int. J. Eloctrochem.

Sic.V0l.9.pp.593-609. Fontana and Green, 1978, ''Corrosion Engineering'', McGrow – Hill Book Company.Gaurav Solanki,2012,''Ueses of High Copper Amalgam Alloys in Dentistry''Int.J.Drug

Res. Tech.Vol.2, No3.pp.222-224.''Guide to Dental Materials and Devices'', 1974 – 1975,7th edition, (A.D.A.). M.lglesias,E. Sorensen and M.Carter. 1984''Some Properties of High Copper Amalgam

Alloys Comparing Hand and Mechanical Trituration' 'The Journal of Dentistry,Vol.52,N0.2.

Marek, 1990, ''The Effect of Tin on The Corrosion Behavior of The Ag – Hg Phase of Dental Amalgam and Dissolution of Mercury'', J Det Res, Vol. 69 No. 12, pp1786-

Fathi M.and V. Mortazavi, 2004, ''A Review on Dental Amalgam Corrosion and Its Consequences'', Journal of Research in Medical Sciences, Vol. 1, pp 42 – 51 .

Tolou, N.2013,2013,''The Effect of Adding TiO2 Nanoparticals on Dental Amalgam''Iranian Journal of Materials Vol.10,No.2.

Razavi, Sh. Mirdamadi and Mormozi, 2011''Investigation The Physical and Mechanical Properties of High Copper and Silver Dental –Filling Amalgam Alloys'' Iranian J.of Materials .Vol.8 No.1.

Robert and Craig, 1992,''The Restorative Dental Materials''The C.V. Mosby Company.

879


Table 1: Chemical Composition of Synthetic Saliva (Marek,1990).NO.Constituentgm/I

1KCL1.52NaHCO31.53NaH2PO4 H2O0.54KSCN0.55Lactic Acid0.9

Table 2: Creep, Dimensional Change and Hardness of Amalgams.Specimens

CodeAdditive Al2O3

(wt%)Creep (%)Dimensional

Change (µm/Cm2)

Hardness (HV)

Am- 0O.OO.654.14133.96Am- 0.10.10.544.52181.88Am- 0.2O.20.235.90187.25Am- 0.3O.30.4311.80227.70Am- 0.4O.40.448.05241.55

Table 3:Values of Corrosion Current Density ,Corrosion Potential and Corrosion Rate.Specimens

CodeAdditive

Al2O3

(wt%)

(µA/cm2)) Improvement (%)

E corr. (mV)

Improvement (%)

Corrosion Rate (mpy)

Am- 00.01.270-535.800.97Am- 0.10.12.210-401.4251.49Am- 0.20.20.5160-646.300.34Am- 0.30.31.0716-507.250.72Am- 0.40.40.5755-472.6120.38

Fig. 1: Polarization Curve of Amalgam (Am- O)

880


Fig. 2: Polarization Curve of Amalgam (Am- O.1)


881




882


(a)

(b) (c)

(d) (e)

Fig.6: Microstructure of amalgams with different weight percentages of (Al2O3). a- Am- 0 b- Am- 0.1 c- Am- 0.2 d- Am- 0.3 e- Am- 0.4

883

€¦ · Web view · 2014-12-22studied uses of high copper amalgam alloys in dentistry , ......

Documents

Transcript of €¦ · Web view · 2014-12-22studied uses of high copper amalgam alloys in dentistry , ......